Photos

Opening the case

There are two screws underneath the rubber feet at the front of the device. Remove those.

Two additional screws are freely removeable at the bottom of the case. Don't forget these

Remove the top of the case with the transparent plastic piece.

Serial

The serial port is located between the FCC logo and the CE logo.
It's pinout is fairly documented by the PCB print: GND|RX|TX|VCC(3.3) (direction as seen from the front of the device).
The bootloader (U-Boot) and the original Asus firmware use a baudrate of 57600 with 8N1.

Compiling OpenWrt

NOTE: OpenWrt currently support this device only since attitude_adjustment.